Factor completely. $4x^2-1=$
Explanation: Both $4x^2$ and $1$ are perfect squares, since $4x^2=({2x})^2$ and $1=({1})^2$. $4x^2-1 = ({2x})^2-({1})^2$ So we can use the difference of squares pattern to factor. ${a}^2 - {b}^2 =({a}+{b})({a}-{b})$ In this case, ${a}={2x}$ and ${b}={1}$ : $({2x})^2 - ({1})^2 =({2x}+{1})({2x}-{1})$ In conclusion, $4x^2-1=(2x+1)(2x-1)$ Remember that you can always check your factorization by expanding it.